Why are stoplights Red, Yellow and Green?
[ 2006-04-27 11:26 ]
 Stoplights are red, yellow, and green,
because traffic officials, early on copied the code system
railroad engineers devised for track systems
controlling the trains.
The goal of the railroad engineers in crafting this code
was to prevent often fatal train collisions, by giving the
trains advance warning. Therefore they did not take their task
lightly in selecting the symbolic colors for the signals.
Red, the color of blood, proved a logical choice for the
stop signal, as for thousands of years, this color forbade
danger. The color alone, railroad engineers reasoned, should
give people cause to pause, to abide by the signal, and to
stop or suffer the consequences of death and destruction.
Engineers used the trial and error method in
selecting the other colors. The first trial in the 1830s, that
of choosing green for the caution signal, and clear for
the go signal, failed miserably. Clear as a choice for the go
signal, varied slightly from the light cast from typical
street lamps, or from the glare of the sunlight, and, thus
could quite easily be mistaken for the go signal...after the
fact.
This failure prompted the railroad engineers to alter their
color selections to red for stop, green for go, and yellow for
caution. Railroad engineers, not traffic engineers, should be
credited for the lives saved in the interim, by their system
of coding warning signals red, yellow, and green.
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track systems: 編碼系統
trial and error:
反復試驗
clear: 明亮的燈
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